Index: wp-includes/ms-functions.php
===================================================================
--- wp-includes/ms-functions.php	(revision 20479)
+++ wp-includes/ms-functions.php	(working copy)
@@ -455,7 +455,7 @@
 	if ( in_array( $user_name, $illegal_names ) == true )
 		$errors->add('user_name',  __( 'That username is not allowed.' ) );
 
-	if ( is_email_address_unsafe( $user_email ) )
+	if ( is_email_address_unsafe( $user_email ) && !is_super_admin() )
 		$errors->add('user_email',  __('You cannot use that email address to signup. We are having problems with them blocking some of our email. Please use another email provider.'));
 
 	if ( strlen( $user_name ) < 4 )
@@ -474,7 +474,7 @@
 		$errors->add('user_email', __( 'Please enter a correct email address.' ) );
 
 	$limited_email_domains = get_site_option( 'limited_email_domains' );
-	if ( is_array( $limited_email_domains ) && empty( $limited_email_domains ) == false ) {
+	if ( is_array( $limited_email_domains ) && empty( $limited_email_domains ) == false && !is_super_admin() ) {
 		$emaildomain = substr( $user_email, 1 + strpos( $user_email, '@' ) );
 		if ( in_array( $emaildomain, $limited_email_domains ) == false )
 			$errors->add('user_email', __('Sorry, that email address is not allowed!'));